Just use gprof?

One piece of advice you'll often encounter is to use the venerable gprof, the precursor of all sampling profilers, because it will already be there in your MinGW installation. It's easy to integrate gprof with Qt Creator, but really, it's only useful for the simplest of cases, because it doesn't support multithreaded programs and dynamically loaded libraries. So, for any serious performance work, its standard version is simply not usable.